1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to automatically setting coarseness in a video display apparatus, and more particularly, to automatically setting coarseness in a video display apparatus when a video signal input from an external apparatus, such as a personal computer (PC), is displayed on a screen.
2. Description of the Related Art
FIG. 1 is a flowchart illustrating a related resolution setting method in a video display apparatus.
In FIG. 1, if a video signal is input from an external apparatus (S10), the video display apparatus may determine a resolution of the input video signal using a horizontal synchronizing signal (H Sync) and a vertical synchronizing signal (V Sync) of the input video signal (S11). The video display apparatus may also determine whether or not the resolution of the input video signal is equal to a preset resolution (S12). If it is determined that the resolution of the input video signal is equal to a preset resolution, the input video signal may be displayed on a screen based on the set resolution (S16).
If it is determined that the resolution of the input video signal is not equal to the preset resolution in operation S12, the video display apparatus may determine whether a resolution stored in the video display apparatus is equal to the resolution of the input video signal (S13). If it is determined that a resolution stored in the video display apparatus is equal to the resolution of the input video signal, the video display apparatus may convert the preset resolution into the resolution of the input video signal (S14), and may display the input video signal on the screen (S16).
Alternatively, if it is determined that a resolution stored in the video display apparatus differs from the resolution of the input video signal in operation S13, the video display apparatus may convert the present resolution into a resolution close to the resolution of the input video signal (S15), and may display the input video signal on the screen (S16). For example, if the input video signal has a resolution of 800*600 (62 Hz), and if a resolution of 800*600 (60 Hz) closest to the resolution is stored in the video display apparatus, the input video signal may be displayed on the screen at the resolution of 800*600 (60 Hz).
Accordingly, the horizontal (H) position, vertical (V) position and coarseness of the input video signal may deviate off the edge of the screen, and in the worst situation no video signal may be displayed on the screen. In order to solve the problems, the video display apparatus has an automatic setting function to automatically set the H position, V position and coarseness. When the automatic setting function is performed, the coarseness setting may differ according to the type of video signal.
FIGS. 2A and 2B are diagrams showing related video signals transmitted to the video display apparatus.
FIG. 2A is a normal timing diagram of an input video signal. The input video signal shown in FIG. 2A has 2240 pixel clocks for a single screen, and 1680 pixel clocks for an active area, in which video is currently displayed on the screen. Additionally, the H Sync of the input video signal has negative polarity, and the V Sync of the input video signal has positive polarity.
FIG. 2B is an offset timing diagram of an input video signal. Such an input video signal is generally used in a flat type video display apparatus. The input video signal shown in FIG. 2B has 1840 pixel clocks for a single screen and 1680 pixel clocks for an active area of the screen. The H Sync of the input video signal has positive polarity, and the V Sync of the input video signal has negative polarity.
The pixel clocks of the video display characteristics are used to convert a received analog video signal into a corresponding digital video signal, and are set as a coarseness value in the video display apparatus.
FIG. 3 is a flowchart illustrating an automatic coarseness setting method in a related video display apparatus.
In FIG. 3, if a user inputs an automatic adjustment command to the video display apparatus (S20), the video display apparatus may detect a pixel clock of the input video signal (S21), and may determine whether the pixel clock of the input video signal corresponds to a preset coarseness value (S23). If it is determined that the pixel clock of the input video signal differs from the preset coarseness value, the video display apparatus may determine whether the pixel clock of the input video signal is contained in a coarseness adjustment range (S25).
If it is determined that the pixel clock of the input video signal is contained in the coarseness adjustment range in operation S25, the preset coarseness value may be changed to a coarseness value corresponding to the pixel clock of the input video signal (S27). On the other hand, if it is determined that the pixel clock of the input video signal is not contained in a coarseness adjustment range in operation S25, the preset coarseness value may be changed to a default value (S29).
For example, assuming that the default value, minimum value and maximum value are set to 2240, 2160 and 2320, respectively, in a first coarseness adjustment range, if a coarseness value of 2150 is preset in the video display apparatus and if a pixel clock of an input video signal is set to 1900, the input video signal may be displayed on the screen at the default value of 2240 in the first coarseness adjustment range. Accordingly, a portion of the input video signal may deviate off the edge of the screen.
Alternatively, assuming that the default value, minimum value and maximum value are set to 1840, 1760 and 1920, respectively, in a second coarseness adjustment range, if a coarseness value of 1900 is preset in the video display apparatus and if a pixel clock of an input video signal is set to 2150, the input video signal may be displayed on the screen at the default value of 1840 in the second coarseness adjustment range. Accordingly, the input video signal may be displayed at a size smaller than the original size, without covering the entire screen.
If the input video signal is not in compliance with the Video Electronics Standards Association (VESA) standard, it is impossible to clearly distinguish whether an input video signal is applied with normal timing or with offset timing, so the above-described problems may be aggravated.